By Justin Parkinson
BBC News political reporter, in Brighton
Energy prices are rising far faster than wages, unions warn
Trade unions are urging the government to impose windfall taxes on "greedy" energy firms to help households struggling to pay fuel bills.
The TUC's annual conference in Brighton backed a motion saying the government needs a "coherent" policy.
It criticises the "big six" energy firms for making £1.6bn last year, while raising prices by 42% this year.
The vote came shortly before Chancellor Alistair Darling was due to give his speech to delegates.
The motion, proposed by the GMB union and seconded by the National Union of Mineworkers, claims that the rising cost of living is causing many people to make a choice between "food or fuel".
It "condemns the actions of these supplies, and the phony competition between the energy companies".
The motion also criticises the regulator Ofgem as "inadequate" and accuses it of "not standing up for consumers".
Tony Woodley, joint general secretary of the Unite union, told delegates: "Time and time again our government rolls over in front of these vested interests."
He added: "Gordon, you've written a book about courage. Take the words out of the page... bring in a windfall tax for our people now."
The demand for a windfall tax on energy companies' profits has also received indications of support from an estimated 100 Labour MPs.
Mr Darling has previously said he has "serious reservations" about the idea.
The government appears to have ruled out a windfall tax for the moment, but wants energy firms to contribute towards a scheme to improve home insulation, cutting wastage and reducing bills.
An announcement is expected this week.
On Monday the TUC conference voted overwhelmingly for a series of national demonstrations against the government's pay policy, which calls for annual increases to be limited to 2% a year.
Unions argue that the real rate of inflation, pushed up by increasing fuel and food costs, is nearer 5%.